JP4278824B2 - Radioactive material storage equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a radioactive substance storage facility such as a radioactive object storage container and a radioactive shielding structure for shielding radiation emitted from a sealed body sealed with a radioactive substance, and in particular, prevents deterioration of the shield due to heat and external atmospheric conditions. In addition, the present invention relates to a radioactive material storage facility that is excellent in radiation shielding performance and durability and easy to maintain with little damage due to external loads.
[0002]
[Prior art]
There are plans to disassemble spent fuel assemblies generated from nuclear power plants and reprocess them to recover useful materials that can be used again as fuel, such as plutonium. Conventionally, such spent fuel has been primarily stored in the fuel assembly pool of the nuclear reactor until reprocessing, but the capacity of storage facilities such as the pool is increased by the spent fuel that increases year by year. May reach the limit. Therefore, there is a need for equipment that can store spent fuel for a long period of time in a safe, inexpensive, and removable state until reprocessing.
[0003]
Development of a dry method for natural cooling by air as such equipment has been promoted, and attention is paid to the fact that the operation cost is lower than that of a pool.
The dry method is roughly classified into two methods, a method using a welded sealed metal container (hereinafter referred to as a canister) and a metal cask method similar to a transport canister. The canister method can be further divided into a vault method in which a large number of canisters are shielded by one storage facility, and a silo or concrete cask method in which one canister is shielded by one concrete structure. Each method has advantages and disadvantages, but in recent years, the concrete cask method has attracted attention because of its low cost. 3 and 4 show schematic cross-sectional views in the horizontal and vertical directions of a concrete module used in the conventional concrete cask method.
[0004]
The concrete module 30 basically includes a canister 31 and a concrete shield 32. The canister 31 has a welded and sealed structure in which a plurality of spent fuel assemblies are enclosed. The canister 31 has a structure in which the enclosed radioactive material does not leak to the outside, and is formed in a cylindrical shape. The canister 31 is loaded in a cylindrical concrete shield 32. A constant gap that forms a cooling air flow path 33 is provided between the canister 31 and the shield 32. In order to introduce external air into the cooling air channel 33, a cooling air inlet 34 is provided on the bottom side of the shield 32, and a cooling air outlet 35 is provided on the upper side of the shield 32. Further, a metal liner 36 is provided on the inner surface of the cooling air passage 33 of the shield 32.
[0005]
Usually, spent fuel is accompanied by heat generation and radiation associated with decay heat. Therefore, the concrete module 30 needs to cool spent fuel, shield radiation, and seal radioactive materials. In the concrete cask method, the cooling is air flowing through the cooling air flow path 33 between the canister 31 and the shield 32, the shield is secured by the shield 32, and the sealing is secured by the canister 31. Further, the strength of the concrete module 30 is also secured by the shield 32. Here, the radioactive material does not leak to the outside when sealed, the radiation dose inside or outside the storage facility is below the standard value stipulated by the law for shielding, and the surface of the canister is stored during the storage period for cooling. It is required that the temperature and the temperature of the concrete shield 32 do not adversely affect the properties of the canister and concrete.
[0006]
By the way, in the conventional concrete shield, the outer surface is at room temperature, but the inner surface becomes high temperature due to decay heat from the spent fuel, and the temperature difference between the inner and outer surfaces increases, resulting in thermal stress (compression at the inner periphery). Stress, tensile stress at the outer peripheral portion), and the tensile stress at the outer peripheral portion is often larger than the tensile strength of the concrete, which causes cracks at the outer peripheral portion. A shield that has excessively cracked has a problem that durability and radiation shielding performance are lowered, making it unsuitable for use.
In order to prevent the influence of cracks due to heat, for example, as a well-known technique, there is a method of introducing a pre-stress and canceling a tensile force due to thermal stress. Japanese Patent Application Laid-Open Nos. 7-27897 and 8-43591 disclose a structure in which a heat pipe is disposed between a canister and a shield or inside the shield. In such a structure, the prestress introduction method is technically possible, but it is expensive, and it can be expected that the increase in the internal temperature of the concrete shield will be suppressed to some extent by using a heat shield plate or heat pipe. It is difficult to prevent cracks that occur on the outer surface of the concrete shield due to temperature difference between the inner and outer surfaces and drying shrinkage of the concrete, and aging deterioration of the concrete (neutralization, infiltration of salt, etc.) that progresses from the outer surface. There was a problem of high cost.
[0007]
Not only the problem of deterioration due to such temperature difference, but also in the conventional reinforced concrete radioactive material storage equipment, the concrete shield is placed in a high temperature environment, so moisture in the concrete is gradually lost due to drying, and against neutron radiation Although the shielding effect is a long span, there is a common problem that it decreases with time.
For this reason, there has been a demand for a radioactive material storage facility that is low in cost, has no deterioration in shielding performance over a long period of time, has excellent durability, and is excellent in safety against external loads.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of such a background, the purpose of the present invention is to effectively prevent cracks and moisture loss that affect the radiation shielding performance of the concrete shield, An object of the present invention is to provide a radioactive material storage facility that is capable of maintaining the radiation shielding ability for a long period of time and is less damaged by an external load and has excellent durability.
[0009]
[Means for Solving the Problems]
As a result of intensive studies, the inventors have covered the above-mentioned problem by covering the outer peripheral surface of a cylindrical concrete shield with a lining material such as a steel plate and arranging a partition plate for inducing temperature cracks in the vicinity of the outer peripheral portion. The present invention has been completed by finding that it can be solved.
That is, the radioactive substance storage facility of the present invention surrounds the outside of the sealing body sealed with the radioactive substance with a cylindrical concrete shield, and provides an air inflow space between the sealing body and the shield. In the radioactive material storage facility that removes heat generated by the radioactive material by the air flowing in the inflow space, the outer periphery of the cylindrical concrete shield is covered with a lining material such as steel, and in the vicinity of the outer periphery, A bent shape for inducing a thermal crack so as to contact with the lining material , preferably arranged so as to have a portion arranged in a direction not at 0 ° and 90 ° with respect to the radial direction of the concrete shield. It is characterized by arranging a partition plate. The surface of the partition plate is preferably provided with irregularities.
[0010]
According to the present invention, the lining material covering the outer periphery of the concrete shield plays a role of restraining the internal concrete, and the strength can be improved, and the loss of moisture from the concrete surface can be reduced by providing a coating layer on the outer periphery. It can suppress, and the fall of the shielding effect with respect to the neutron beam accompanying the loss of moisture can be prevented. Further, a bend for inducing a temperature crack so as to have a portion disposed in the vicinity of the outer periphery of the cylindrical concrete shield in a direction other than 0 ° and 90 ° with respect to the radial direction of the concrete shield. By arranging the partition plate in the shape, it is possible to induce temperature cracks along this partition plate, prevent penetration cracks that affect the radiation shielding performance, etc., and to prevent radiation passing between the cracks. Transmission can be prevented.
In the radioactive substance storage facility of the present invention, the membrane structure element is provided as a membrane structural element to a lining material such as a metallic liner covering the outer periphery of a cylindrical concrete shield, and further, a cylindrical shape is provided. It is preferable to take the aspect which improves the resistance with respect to external loads, such as an earthquake, by arrange | positioning the reinforcement bar | burr of the circumferential direction and a perpendicular direction in the inner area | region of a concrete shielding body.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
The radioactive substance storage facility of the present invention comprises a cylindrical concrete shielding body formed by covering the outer peripheral surface of a sealing body sealed with a radioactive substance with a lining material and upper and lower disks, and the sealing An air inflow space is provided between the body and the shield, heat generated by the radioactive material is removed by the air flowing in the air inflow space, and a metal lining material constituting the cylindrical shield, and preferably Is a concrete structure that resists external stresses such as earthquakes acting on the radioactive material storage equipment and thermal stress due to the temperature difference between the inside and outside surfaces of the concrete shield, by means of concrete provided with a reinforcing structure with reinforcing bars inside.
[0012]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 show a schematic diagram in the horizontal direction and a schematic sectional view in the vertical direction of the radioactive substance storage facility 10 according to the first embodiment of the present invention. The radioactive substance storage facility 10 includes a canister 11 and a concrete shield 12. The canister 11 has a cylindrical shape, and a radioactive substance is sealed inside.
[0013]
The concrete shield 12 includes a cylindrical portion 12a made of reinforced concrete whose outer peripheral surface is covered with a lining material 13, a thick disk (lower lid) 12b that supports the cylindrical portion 12a, and an upper lid 12c of a canister loading / unloading port. Yes.
A gap between the inner diameter of the shield 12 and the outer diameter of the canister 11 functions as a cooling air flow path 14.
[0014]
As the lining material 13 used for the outer periphery, a known material, for example, a metal plate such as a steel plate, a molded body such as a high-strength engineering plastic or a fiber-reinforced plastic, a band shape reinforced with carbon fiber or high-strength polyamide fiber, or the like. It is possible to select and use a lining material made by winding a resin plate or a metal plate, but considering strength and durability, steel plates such as general structural rolled steel and welded structural rolled steel Etc. are preferable. Moreover, although there is no restriction | limiting in particular in the thickness of a lining material, when using a steel plate, from a viewpoint of an effect and economical efficiency, generally it is preferable that it is the range of 5-20 mm, Furthermore, 10- A range of 15 mm is preferred. If the thickness of the liner 13 is too thin, the effect of improving the strength is insufficient, and if it is too thick, it is not preferable from the viewpoint of economy.
[0015]
Under the shield 12, one or a plurality of cooling air passages 15 for communicating the outside of the shield with the cooling air passages 14 are formed. The inlet side cooling air flow path 15 includes a first horizontal portion formed horizontally on the outside, a vertical portion extending upward from an inner end portion of the first horizontal portion, and an inner side from an upper end portion of the vertical portion. It is comprised from the 2nd horizontal part extended to. The upper surface of the first horizontal portion is located on the same plane as the lower surface of the second horizontal portion or below the lower surface of the second horizontal portion, so that the radiation passing through the second horizontal portion is reflected by the wall surface of the bent portion. So that it does not leak outside. Each horizontal portion may be inclined upward as it goes inward.
A plurality of projections (not shown) are formed inside the cooling air channel 15 on the inlet side of the shield 12, and the canister 11 is supported by the shield 12 by these projections.
[0016]
Further, a cooling air flow path (outlet side) 16 is formed at a position facing the cooling air flow path (inlet side) 15 formed on the lower side of the shielding body at the upper part of the shielding body 12. The cooling air flow path (exit side) 16 has a first horizontal portion formed horizontally inside, a vertical portion extending upward from an outer end portion of the first horizontal portion, and horizontally extending from an upper end portion of the vertical portion to the outer side. It is comprised from the 2nd horizontal part extended to. The upper surface of the first horizontal portion is located on the same plane as the lower surface of the second horizontal portion or below the lower surface of the second horizontal portion, so that the radiation passing through the first horizontal portion is reflected by the wall surface of the bent portion. So that it does not leak outside. Each horizontal portion may be inclined upward as it goes outward.
A lining material 13 is attached to the inside of the cooling air channel (inlet) 15 and the cooling air channel (outlet side) 16.
In addition, in order to suppress deterioration due to the temperature rise of the shield 12, a heat insulating material such as a ceramic system can be installed on the lining material 17 on the inner peripheral surface facing the canister 11 as necessary.
[0017]
Cooling air is introduced from the cooling air flow path (inlet) 15 to the lower side of the shield, cools the canister 11 loaded in the shield 12 when passing through the cooling air flow path 14, and is shielded by natural convection. The body is raised and exhausted from the cooling air flow path (exit side) 16. In this process, decay heat emitted from the radioactive material in the canister 11 is discharged to the outside by natural convection of air passing through the cooling air flow path 14, and a part of the decay heat is the concrete constituting the concrete shield 12. Is transmitted to.
According to the present invention, the surface of the cylindrical concrete shield 12a is covered with a lining material 13 such as a steel plate, and can prevent deterioration in durability due to neutralization of concrete, intrusion of flying salt, and the like. In addition, since moisture in the concrete does not escape to the outside, it is possible to prevent a decrease in shielding performance against neutron beams and the like.
[0018]
In this embodiment, a portion arranged in the radial direction of the cylinder in the vicinity of the lining material 13 that covers the outer peripheral surface of the cylindrical shield 12a, in directions that are not 0 ° and 90 ° with respect to the radial direction of the concrete shield. A folding screen-like partition plate 18 is provided so as to contact the lining material 13 covering the outer peripheral surface. By inducing temperature cracks along the bent partition plate 18, linear transmission of radiation through the cracks can be prevented and shielding performance can be ensured.
The partition plate 18 is desirably installed so as to equally divide the cylindrical portion 12a in the circumferential direction, and the number of installation locations is considered to be about 6 to 8, but is not limited thereto. In this embodiment, the partition plate 18 has a folding screen shape. However, if the partition plate 18 has a bent shape, it canister against the temperature crack of concrete that may occur in the vicinity of the partition plate. As long as the radiation emitted from 11 has a size that does not pass through the temperature crack, the shape is not particularly limited, and a wave shape, folding screen shape, or any bent shape equivalent to these can be selected.
Considering these, it is preferable that the partition plate 18 has a thickness of about 10 to 20 mm and a bending pitch of about 100 to 300 mm.
[0019]
Moreover, it is preferable to provide unevenness on the surface of the partition plate 18 in order to prevent the partition plate and the concrete from being displaced and to transmit the shearing force of the concrete. Examples of the irregularity include an aspect in which disc-shaped convex portions having a thickness of about 5 to 10 mm and a diameter of about 20 to 30 mm are provided on the surface of the partition plate at a pitch of about 50 mm.
As the material of the partition plate 18, considering the ease of processing of the unevenness and bending shape to be formed, the workability at the time of constructing the radioactive substance storage facility, and the shielding performance against various radiations, cement-based molded plates such as fiber reinforced mortar and ceramics It is appropriate to use an inorganic material such as a molded plate. It is also possible to use a steel plate having a predetermined uneven shape.
[0020]
In this aspect, the structure of the shield of the reinforced concrete structure is adopted in order to ensure the strength. In the inner region of the cylindrical concrete shield 12a, the circumferential reinforcing bar 19 and the vertical reinforcing bar 20 are provided. Is arranged. In this way, when the bent partition plate 18 is arranged on the cylindrical shield 12a having the reinforced concrete structure, as shown in FIG. 2, the partition plate 18 is arranged in the vicinity of the outer peripheral portion of the cylindrical shield 12a. In addition to preventing cracks, reinforcing reinforcing bars 19 and 20 may be provided near the inner periphery. By setting it as such a structure, the cylindrical part 12a can be utilized as a resistance element with respect to an earthquake load. Further, by using the lining material 13 on the outer peripheral surface of the shield 12a as a membrane structural element and imparting a role of restraining the internal concrete, the resistance to cracking and external force can be improved.
[0021]
With such a structure, the outer region of the concrete shield cylindrical portion 12a mainly contributes to radiation shielding, and the inner region becomes a region having two functions of radiation shielding and a resistance element at the time of earthquake. These divisions, that is, the length and number of the partition plates 18, the strength (thickness and material) of the reinforcing bars, the position of the arrangement, and the arrangement pitch depend on the temperature conditions received by the concrete shield and the seismic performance to be applied. What is necessary is just to decide suitably.
[0022]
Here, the manufacturing method of this cylindrical concrete shielding body 12a is demonstrated. When the cylindrical shield 12a is formed, the lining material 13 and the metal liner 17 are used as a mold, reinforcing reinforcing bars 19 and 20 are arranged inside, and the metal liner 17 and the outer periphery of the inner peripheral portion are disposed. The lining material 13 is fixed with a tie bar or the like so as to have a fixed interval, and a double cylinder formed by the lining material 13 and the metal liner 17 is used as a mold to form a shielding body therein. Concrete for this purpose is placed and cured to produce a cylindrical concrete shield 12a. At this time, the partition plate 18 also has a portion arranged in advance in a direction other than 0 ° and 90 ° with respect to the radial direction of the concrete shield , and is in contact with the lining material covering the outer peripheral surface. By arrange | positioning to, the integration with the partition plate 18 and internal concrete can be aimed at.
According to this method, since the lining material 13 and the metal liner 17 also serve as a formwork at the time of placing concrete, no formwork material is required, and the construction period can be shortened.
[0023]
As the concrete constituting the shield 12 of the present invention, known ones can be used as appropriate. For example, a cement and fine aggregate / coarse aggregate are sequentially added to a mixer, and the number thereof is several. After kneading for a second, if necessary, additives such as cement dispersant and water reducing agent are added together with water and kneaded, and the resulting paste-like concrete composition is cast into a mold and manufactured. Is mentioned.
[0024]
Here, as usable cement, various mixed cements such as blast furnace cement, fly ash cement, and silica fume cement can be used in addition to various portland cements such as ordinary cement, early-strength cement, and moderately hot portland cement.
Further, if necessary, inorganic powders such as blast furnace slag fine powder, meteorite powder, limestone powder, and silica fume fine powder can be added to these cements within a range not impairing the effects of the present invention. .
[0025]
In the production of concrete shields, the use of expansive concrete during solidification constrains expansion by the surrounding lining material, so a compressive force is introduced into the concrete shields to prevent and reduce temperature cracks. It is effective. Examples of such expansive concrete include expansive concrete to which an expansive agent mainly composed of alumina powder is added.
[0026]
As an advantage of the above embodiment, the surface of the radioactive material storage container is covered with a lining material, and the concrete surface is not exposed, so that the durability is improved, and since the lining material is present on the outer peripheral surface, an external load such as an earthquake is applied. Even if it is damaged, there is little damage and cracks are not exposed, so there is a high possibility that it can be used continuously after a disaster such as an earthquake, and the entire storage container is covered with lining material, so maintenance and maintenance However, regular steel plate coating is sufficient, maintenance is easy, and the lining material on the outer peripheral surface prevents the moisture from escaping in the concrete, so the shielding effect against neutrons, etc. is maintained over a long period of time. Point.
[0027]
【The invention's effect】
According to the radioactive substance storage facility of the present invention, it is possible to prevent the deterioration of the concrete shield due to the heat generated by the canister, and to construct a radioactive substance storage facility that is excellent in durability and shielding performance over a long period of time and easy to maintain.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view in the horizontal direction of a radioactive substance storage facility according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view in the vertical direction of the radioactive substance storage facility of FIG.
FIG. 3 is a schematic cross-sectional view in the horizontal direction of a conventional radioactive substance storage facility.
FIG. 4 is a schematic sectional view in the vertical direction of the radioactive substance storage facility of FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Radioactive substance storage equipment 11 Canister 12 Concrete shielding body 12a Cylindrical concrete shielding body 12b Shield lower cover 12c Shield upper cover 13 Lining material (outer peripheral surface)
14 Gap (cooling air flow path)
15 Cooling air flow path 16 on the inlet side Cooling air flow path 17 on the outlet side Metal liner (inner peripheral surface)
18 Partition plate 19 Reinforcing bar in circumferential direction 20 Reinforcing bar in vertical direction

Claims (4)

The outside of the sealing body sealed with the radioactive material is surrounded by a cylindrical concrete shield, an air inflow space is provided between the sealing body and the shielding body, and the radioactive material is caused by the air flowing inside the air inflow space. In a radioactive material storage facility for removing generated heat, the outer periphery of the cylindrical concrete shield is covered with a lining material, and temperature cracks are induced in the vicinity of the outer periphery of the cylindrical concrete shield. A radioactive substance storage facility, wherein a partition plate having a bent shape is disposed so as to have a portion disposed in a direction other than 0 ° and 90 ° with respect to a radial direction of the concrete shield.   The radioactive substance storage facility according to claim 1, wherein the partition plate having a bent shape for inducing the temperature crack is disposed in contact with the lining material.   The radioactive material storage facility according to claim 1 or 2, wherein reinforcing bars in a circumferential direction and a vertical direction are arranged in an inner region of the cylindrical concrete shield.   The radioactive substance storage facility according to any one of claims 1 to 3, wherein an uneven surface is provided on the surface of the bent partition plate.

Images